Shearing Cutter on a Degradation Drum

ABSTRACT

In one aspect of the present invention, a pick comprises a forward end and rearward end. The forward end comprises a shearing cutter and the rearward end comprises a shank. The shank and the shearing cutter are arranged co-axially about a central axis. The shearing cutter is supported by an enlarged section that narrows towards the shearing cutter and that has a greater cross section than the shank along a plane substantially perpendicular to the central axis. The shearing cutter comprises a flat surface that is substantially perpendicular to the central axis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/424,806 filed on Jun. 16, 2006. This application claims priority toU.S. application Ser. No. 11/424,806, which is herein incorporated byreference for all that it teaches.

BACKGROUND OF THE INVENTION

The present invention relates to a cutting tool that may be used inasphalt, mining, excavation, and other industries. In asphalt orconcrete milling, an array of cutting tools supported by a drum mayengage the paved surface causing both the paved surface to degrade, andthe tools to wear. Typically, conical cutting elements are used inmilling. These conical cutting elements are rotationally supported by ablock or drum on a milling drum. The blocks are generally adapted tohold the picks at an offset angle such that the picks will rotate asthey engage the formation. Rigidly fixed shearing cutters have also beenused in the milling drum prior art.

U.S. Pat. No. 5,235,961 to McShannon, which is herein incorporated byreference for all that it contains, discloses a carbide mineral cuttingtip with a solid carbide body having at least one front face, at leastone top face, a bottom seating face, a rear face, and side faces, therear face being provided at the end of an extended tail portion of thetip, whereby the front-to-rear length of the tip approximates to twicethe depth of the tip represented by the top-to-bottom length of thefront face. The invention also includes a mineral cutter pick providedwith such a tip.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, a pick comprises a forward endand rearward end. The forward end comprises a shearing cutter and therearward end comprises a shank. The shank and the shearing cutter arearranged co-axially about a central axis. The shearing cutter issupported by an enlarged section that narrows towards the shearingcutter and that has a greater cross section than the shank along a planesubstantially perpendicular to the central axis. The shearing cuttercomprises a flat surface that is substantially perpendicular to thecentral axis.

The pick may be secured within a holder attached to a drum. The shankmay be rotatably secured within a bore and may be rotatable about acentral axis of the shank. The forward end may be tapered towards theshearing cutter. The shearing cutter may comprise cemented metalcarbide. The shearing cutter may also comprise a super hard materialbonded to cemented metal carbide at a non-planar interface, the superhard material forming the flat surface. The super hard material maycomprise an axial thickness greater than the thickness of the cementedmetal carbide. The shank may be press fit into the bore of the holder.The shearing cutter may be brazed to a carbide bolster thatprogressively increases in diameter from the forward end. The shearingcutter may be bonded to a carbide bolster attached to a rotating shield.

The pick may be incorporated in a milling machine. The pick may beincorporated in mining machine. The shearing cutter may comprise a flatedge, rounded edge, chamfered edge, double chamfered edge, orcombinations thereof. The pick may also be incorporated in a trenchingmachine.

In another aspect of the present invention, a degradation drum comprisesa pick secured to an outer surface of the drum through a block rigidlymounted to the outer surface. The block comprises a bore with an innersurface, the shank being secured within the bore. At least one pickcomprises a shearing cutter comprising a flat surface. The shearingcutter and the shank are co-axially arranged about a central axis. Theflat surface of the shearing cutter is substantially perpendicular tothe central axis. At least one shearing cutter may be positionedproximate a longitudinal edge of the drum. The bore may be substantiallyaligned with a length of the block and may be substantially coaxial withthe central axis of the pick. The pick may be laterally offset from thedirection of rotation of the drum. The pick may be offset at an angle of7 to 15 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram of an embodiment of a degradationdrum suspended underside of a pavement milling machine.

FIG. 2 is a perspective diagram of an embodiment of a degradation drum.

FIG. 3 is a cross-sectional diagram of an embodiment of a pick.

FIG. 4 is a cross-sectional diagram of an embodiment of a degradationdrum engaged with a portion of a pavement.

FIG. 5 is a cross-sectional diagram of another embodiment of a pick.

FIG. 6 is a cross-sectional diagram of another embodiment of a pick.

FIG. 7 is a detailed diagram of another embodiment of a degradationdrum.

FIG. 8 is a detailed diagram of another embodiment of a degradationdrum.

FIG. 9 is a cross-sectional diagram of another embodiment of a pick.

FIG. 10 is a cross-sectional diagram of another embodiment of a pick.

FIG. 11 is a cross-sectional diagram of another embodiment of a pick.

FIG. 12 is a cross-sectional diagram of an embodiment of a shearingcutter.

FIG. 13 is a cross-sectional diagram of another embodiment of a shearingcutter.

FIG. 14 is a cross-sectional diagram of another embodiment of a shearingcutter.

FIG. 15 is a cross-sectional diagram of another embodiment of a shearingcutter.

FIG. 16 is a cross-sectional diagram of another embodiment of a shearingcutter.

FIG. 17 is an orthogonal diagram of an embodiment of a mining machine.

FIG. 18 is a perspective diagram of an embodiment of a trenchingmachine.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

FIG. 1 is a cross-sectional diagram that shows a plurality of picks 101attached to a driving mechanism, such as a rotatable drum 102 attachedto the underside of a pavement milling machine 103. The milling machine103 may be an asphalt planer used to degrade man-made formations 104such as pavement prior to placement of a new layer of pavement. Thepicks 101 may be attached to the drum 102, bringing the picks 101 intoengagement with the formation 104. A holder, such as a block welded orbolted to the drum 102, is attached to the driving mechanism and a shankof the pick 101 is inserted into the holder. The holder may hold thepicks 101 at an angle offset from the direction of rotation, such thatthe picks 101 engage the formation 104 at a preferential angle. Arrow105 discloses the milling machine's direction of travel.

Referring to FIG. 2, a rotary degradation drum 102 for harder pavements,such as concrete is disclosed. The degradation drum 102 may comprise aplurality of picks 200 disposed adjacent to each other, thereby coveringmost of the outer surface of the drum 102. In some embodiments, the drum102 may comprise as many as 400 picks. The plurality of picks 200 maycomprise shearing cutters 210.

Shearing cutters 210 may have advantages over pointed picks. Forinstances, the shearing cutters 210 may take a shallower depths of cutinto the formation. This makes the shearing cutters 210 less aggressiveand requires a greater specific energy than pointed cutters. But thismay be advantageous when the pick is enhanced with a brittle cuttingmaterial such as sintered polycrystalline diamond or cubic boronnitride. While efficiency is lost, the life of the shearing cutter 210is believed to be longer. Thus, the overall performance of the drum 102may improve for harder formations. Preferably, the picks' shanks arerotatably secured within the drum's holders, and the picks 200 withshearing cutters 210 are laterally offset to encourage the picks 200 torotate upon engagement with the formation. This rotation spreads thewear around the shearing cutter's entire circumference instead oflocalizing wear on a specific side. The picks 200 may be offset at anangle of 7 to 15 degrees from the direction of rotation of the drum 102.The picks 200 disposed in the center region of the drum 102 may beoffset less than picks 200 disposed away from the center region of thedrum 102. Picks 220 positioned at the longitudinal ends of the drum 102may be angled to cause the cutter to rotate as the pick 220 not onlyengages the depth of cut, but also as the cutter engages the wall formedby the cut as the cutter is entering the cut.

FIG. 3 discloses a cross-sectional diagram of an embodiment of a pick200. The pick 200 may comprise a forward end and a rearward end. Theforward end may comprise the shearing cutter 210 and a rearward end maycomprise a shank 300 that is adapted to fit within the bore of thedrum's holder or block. The shank 300 and the shearing cutter 210 arearranged co-axially about a central axis of the pick 200. The shearingcutter 210 is supported by an enlarged section of the pick 200 thatnarrows towards the shearing cutter 210. The tapered end may prevent theforward end of the pick 200 from coming into contact with the formationespecially when the negative rake angle is small as in the case ofshearing cutters 210. The enlarged section has a greater cross sectionthan the shank 300 along a plane that is substantially normal to thecentral axis.

The shearing cutter 210 may comprise shear cutter bonded directly to acemented metal carbide core 380 press fit into a bore 310 formed in theforward end of the pick 200. In some embodiments, the core 380 may besegmented and the distal most segment may support a superhard cuttingmaterial such as sintered polycrystalline diamond or cubic boronnitride. The shearing cutter 210 may comprise a flat surface 330 thatforms a cutting edge with the cutter's cylindrical side. The flatsurface 330 may be substantially perpendicular to the axis of the shank300.

The pick 200 may comprise a gap 340 of 0.010 to 0.115 inches between theouter surface of the shank 300 and the inner surface of the holder 350.The gap 340 may assist the pick's free rotation. Preferably, the gap 340is small enough to prevent dirt and debris from entering while cuttingthe formation. Preferably, the shank 300 comprises at least twodiameters joined by a transition region. The multiple diameters arebelieved to reduce bending forces in the shank 300. Bending forces mayalso be reduced by lengthening the shank 300 and the holder's bore. Thepick 200 may comprise a washer 360 intermediate the forward end and therearward end. The washer 360 may allow the rotation of the pick 200 fora long period of time. The washer may be constructed of steel. The shank300 and the holder 350 may be held together by a snap ring mechanism370.

FIG. 4 discloses a rotatable shearing cutter 210 in contact with aformation 104. The shearing cutter 210 scrapes a thin layer of formation104 off during each pass. This is opposed to pointed cutters that aremore aggressive. Pointed cutters may induce fractures which usuallypropagate through the formations. Since the pointed cutters areimparting more energy into the formation per pass, pointed cutters tendto wear faster. In softer formations, typically made of asphalt, acarbide or superhard material enhanced pointed cutter may be robustenough. However, in harder formations like asphalt formations thatincorporate extremely hard rock or concrete pavement, the traditionalapproach of using a pointed cutter may be costly. By changing the shapeof the cutter to be less aggressive, the impact force experienced by thecutter is less, thereby extending the cutter's life.

The shearing cutters 210 may degrade the formation 104 at a negativerake angle. The rake angel is measured by the angle formed against thetangent of the cut's curvature and the flat surface of the shearingcutter 210. Preferably, the angle is negative 10 to 20 degrees forconcrete jobs of average hardness. More preferably, the angle is 15degrees.

FIG. 5 is a cross-sectional diagram of another embodiment of a pick 200.In some embodiments, the shearing cutter 210 may comprise a super hardmaterial 550 bonded to cemented metal carbide 500 at a non-planarinterface 510. The super hard material 550 may form the flat surface520. The super hard material 550 may comprise a material selected from agroup comprising diamond, polycrystalline diamond, natural diamond,synthetic diamond, vapor deposited diamond, silicon bonded diamond,cobalt bonded diamond, thermally stable diamond, polycrystalline diamondwith a binder concentration of 1 to 40 weight percent, infiltrateddiamond, layered diamond, monolithic diamond, polished diamond, coursediamond, fine diamond, cubic boron nitride, diamond impregnated matrix,diamond impregnated carbide, metal catalyzed diamond, or combinationsthereof.

Preferably, a sintered polycrystalline diamond is used. The sintereddiamond is formed by subjecting a plurality of diamond crystals to highpressure and high temperature. A catalyst is generally used to lower theactivation energy required to form new diamond to diamond bonds betweenthe diamond crystals resulting in a polycrystalline diamond geometry.Sintered diamond is preferred over vapor deposited diamond because vapordeposited diamond is generally not as dense as sintered diamond.Generally, vapor deposited diamond is easier to bond to object, but itexhibits anisotropic properties by having greater impact resistant incertain directions. Sintered diamond, on the other hand, is moreisotropic by having high impact resistance in from all directions.

Referring to FIG. 6, shearing cutter 210 may be bonded to a cementedmetal carbide bolster 600 that increases in diameter moving away fromthe forward end. The carbide bolster 600 may resist abrasion at theforward end of the pick 200.

FIG. 7 discloses a rotary degradation drum 102 specifically tailored forasphalt milling. The drum 102 may comprise a plurality of rotary picks200 arranged in a helical array. The picks 200 may comprise shearingcutters 210. The drum 102 may comprise fewer picks 200 for asphaltmilling in comparison to concrete milling, thereby increasing the impactforces per pick.

FIG. 8 discloses a drum with both pointed cutters and shear cutters. Insome embodiments, the shearing cutter 210 may be positioned proximatethe longitudinal edge of the drum 102 while the pointed cutters arelocated along the length of the drum 102. In some embodiments, the shearcutters 210 may prevent sides of the drum 102 from coming into contactwith formation. In other embodiments, the pointed and shear cutters maybe combined in other arrangements. For example, a shear cutter 210 maybe positioned to follow a pointed cutter, thereby, subjecting someformation area to both cutting mechanism. Here, the pointed cuttingelement aggressively impacts the formation with the force being focusedjust in front of the pointed cutter's apex. The pointed cutterpenetrates easier and induces fractures through the area. The shearcutter 210 follows and opens the cut wider than the pointed cutter.Thereby, removing the fractured area easier since the formation isweakened from the induced fractures. It is believed that thiscombination may be synergistically remove more formation materialtogether than either cutting mechanism may remove on its own.

FIG. 9 discloses the forward end with a carbide bolster 900 attached toa rotating shield 910 and a rearward stationary end comprising a shank920. A bearing between the shield and the shank may provide freerotation. In some embodiments, the rotation may be restricted to reducethe differential movement between the parts and preventing erosionbetween them.

FIG. 10 discloses the forward end of the pick 200 comprising shearingcutter 210 attached to a cemented metal carbide 380. The shearing cutter210 and the cemented metal carbide 380 may comprise same diameter. Theshearing cutter 210 may comprise a superhard cutting material such assintered polycrystalline diamond or cubic boron nitride. In someembodiments, the shearing cutter 210 may comprise a cemented metalcarbide 380 as illustrated in FIG. 11. The shearing cutter 210 bonded tothe cemented metal carbide 380 may be press fit into a bore 310 formedin the forward end of the pick 200. The cemented metal carbide 380 maycomprise a greater axial thickness than the shearing cutter 210.

FIGS. 12-16 disclose different shear cutters 210 comprising a super hardmaterial 550 bonded to cemented metal carbide 500. The bonding betweenthe super hard material 550 and the cemented metal carbide 500 maycomprise planar interface, non-planar interface, or combinationsthereof. The shearing cutters 210 may comprise flat edge 1000, roundededge 1001, chamfered edge 1002, double chamfered edge, or combinationsthereof. The shearing cutters 210 with flat edge 1000 may perform wellin soft formations while the shearing cutters 210 with rounded andchamfered edge may perform better in hard formations by changing thedirection that resultant force loads are induced into the cutter. Insome embodiments, the edge may comprise multiple chamfers that are atdifferent angles with the flat. These different chamfers are preferablycontiguous. In some embodiments, the chamber may not be uniform. FIG. 15discloses a cutter with a carbide that narrows towards the super hardmaterial. FIG. 16 discloses two flats both capable of cutting theformation. The diameter of the distal most flat 1003 comprises a smalldiameter than the more proximal flat 1004, so the more proximal flat1004 may widen a cut formed by the more distal flat 1003. In someembodiments, the super hard material 550 may comprise an axial thicknessgreater than the thickness of the cemented metal carbide 500. In someembodiments, the super hard material 550 may comprise an axial thicknesssmaller than the thickness of the cemented metal carbide 500. In otherembodiments, the super hard material 550 may comprise an axial thicknessequal to the thickness of cemented metal carbide 500.

FIG. 17 discloses a mining machine 1700 incorporating the presentinvention. The picks 101 may degrade a coal steam 1720 or a steam madeof another valuable material or mineral.

FIG. 18 discloses a trenching machine 1800 comprising a plurality ofpicks 101 on a rotating chain 1810. The rotating chain 1810 rotates inthe direction of the arrow 1850 and cuts the formation forming a trenchwhile bringing the formation cuttings out of the trench to a conveyorbelt 1830 which directs the cuttings to a side of the trench. Therotating chain 1810 is supported by an arm.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications apart from those shown or suggested herein, may bemade within the scope and spirit of the present invention.

1. A pick, comprising: a forward end and rearward end; the forward endcomprising a shearing cutter and the rearward end comprising a shank;the shank and the shearing cutter are arranged co-axially about acentral axis; the shearing cutter is supported by an enlarged sectionthat narrows towards the shearing cutter and that has a greater crosssection than the shank along a plane substantially perpendicular to thecentral axis; and the shearing cutter comprising a flat surface that issubstantially perpendicular to the central axis.
 2. The pick of claim 1,wherein the pick is secured within a holder attached to a drum.
 3. Thepick of claim 1, wherein the shank is rotatably secured within a boreand is rotatable about a central axis of the shank.
 4. The pick of claim1, wherein the forward end is tapered towards the shearing cutter. 5.The pick of claim 1, wherein the shearing cutter comprises cementedmetal carbide.
 6. The pick of claim 1, wherein the shearing cuttercomprises a super hard material bonded to cemented metal carbide at anon-planar interface, the super hard material forming the flat surface.7. The pick of claim 6, wherein the super hard material comprises anaxial thickness greater than the thickness of the cemented metalcarbide.
 8. The pick of claim 1, wherein the shank is press fit into thebore of the holder.
 9. The pick of claim 1, wherein the shearing cutteris brazed to a carbide bolster that progressively increases in diameterfrom the forward end.
 10. The pick of claim 1, wherein the shearingcutter is bonded to a carbide bolster attached to a rotating shield. 11.The pick of claim 1, wherein the pick is incorporated in a millingmachine.
 12. The pick of claim 1, wherein the pick is incorporated inmining machine.
 13. The pick of claim 1, wherein the shearing cuttercomprises a flat edge, rounded edge, chamfered edge, double chamferededge, or combinations thereof.
 14. The pick of claim 1, wherein the pickis incorporated in a trenching machine.
 15. The pick of claim 1, whereinthe pick comprises a negative rake angle of 15 degrees approximately.16. A degradation drum, comprising: a pick secured to an outer surfaceof the drum through a block rigidly mounted to the outer surface; theblock comprising a bore with an inner surface, the shank being securedwithin the bore; at least one pick comprising a shearing cuttercomprising a shearing cutter comprising a flat surface; the shearingcutter and the shank are co-axially arranged about a central axis; andthe flat surface of the shearing cutter is substantially perpendicularto the central axis.
 17. The drum of claim 16, wherein the at least oneshearing cutter is positioned proximate a longitudinal edge of the drum.18. The drum of claim 16, wherein the bore is substantially aligned witha length of the block and is substantially coaxial with the central axisof the pick.
 19. The pick of claim 16, wherein the pick is laterallyoffset from the direction of rotation of the drum.
 20. The pick of claim16, wherein the pick is offset at an angle of 7 to 15 degrees.